Reliability analysis of rotorcraft composite structures

This paper develops a probabilistic analysis framework to predict the fatig ue reliability of laminated composites and applies it to tapered composites used in rotorcraft structures. The method combines finite-element analysis , composite laminate analysis, fatigue failure modeling, and first-order re liability analysis to achieve this objective. This methodology is demonstra ted on a composite helicopter rotor hub test specimen with thick, thin, and tapered regions. The specimen is subjected to centrifugal and oscillatory bending loads. The failure mechanism observed for this type of fatigue load ing is an initial tension crack followed by internal delamination at the th ick-to-taper transition, where internal ply drop-offs occur. The proposed m ethod predicts the probability of delamination initiation for such rotor hu bs. The method is validated using full-scale test results.